These guitars are thoroughly inspected and prepared by Martin craftsmen at our factory and carry a limited lifetime warranty. White binding on body (w/b/w/b/w.) Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white. Laminated rosewood sides and 3-piece back, ala' D35.
Other Sigma instruments included mandolins, banjos, acoustic and electric Bass guitar basses and solidbody and Semi-acoustic guitar|hollow body electric guitars. White/pearl binding on body (w/p/w/p/w.) Rosewood overlay on 1st generation "Spatula" headstock (Sigma w/Σ logo.) Headstock and fretboard are single-bound in white.
Some guitars made later in Taiwan and Indonesia have a different headstock shape and decal: The shape is more squared off at the top corners, while the decal states, "Sigma Guitars" on top with a miniature version of the "C. The paper labels for model/serial number identification had also changed again, this time with a fancy border and the word "Sigma" or "Sigma Guitars" printed in gold ink.
The issue of whether or not Sigma guitars are solid wood or "plywood"laminate wood has been a source of controversy and confusion for many years now.
Bridges and tuners may have been installed, as well final sanding and finishing before strings were installed and a final set-up was done. Serial numbers for Sigma guitars built in South Korea, Taiwan and Indonesia are perhaps even more meaningless, though again some seem to indicate the year of manufacture (e.g. Adjustable rosewood bridge to approximately 1975, non-adjustable thereafter.
Because more than 30% of the work was completed within the borders of the United States, Martin was legally allowed to designate them as Made in U. 81XXXXXX.) Since we know these instruments were manufactured from 1984 through 2007 in these three countries, it is safe to assume that a serial number beginning with 81XXXXXX (which I have personally seen) were not produced in 1981 and that these serial number 'indicators' are not to be trusted.
All other text was printed in black ink, or stamped on in ink by the manufacturer (model and serial numbers.) 5-digit, or 8-digit serial numbers. Being a mid-year change, some continued on with the "Purple" label, though with the new serial number designation preceded by an "S" or an "E" This is prefixed by the serial number assigned to the instrument and followed by an ink stamp of the model number. L-R as seen through the sound hole: Serial number, "Brand," Model number.) The serial numbers on these instruments were often preceded by the letters S or E; e.g. It is currently believed that this transition was complete by 1979. It is widely assumed by owners and Sigma historians alike that this is correct, though C. Martin cannot, or will not confirm this."Sigma-Martin USA" guitars built in 19 only, had specifically assigned serial numbers ranging from 900,001 to 902,908 (2,907 in total.) These serial numbers are documented by C. These "N" instruments of which there were only two models ever produced, the DR-28N & DR-35N partially assembled in Japan and were imported to Nazareth ("N") and the Martin guitar factory as "kits". There they were completed and finished alongside the regular Martin production line. The early 70s models (1970 -1975) can be distinguished by a more squared peghead, shaped similarly to that of a "spatula." The logo consisting of a gold decal with the single word in block lettering SIGMA surmounted with the Σ symbol (the Greek letter sigma), in mother of pearl. There were only two models, labeled "Sigma Martin USA DR-28N and DR-35N," "N" for Nazareth. The original factory brochure also states components were processed and finished on the same production line as regular Martins. In 1978, model designations were added to capitalize on Martin model numbers: the DM-18, DM-19, DR-28, DR-28H, DR-35, DR-41, and DR-45. Pegheads & Logos Sigma guitars made in Japan from 1970 through 1983. The affixed warranty card was amended to read..."Your D-10 '9' (or D-10 '8') is not warranted against cosmetic defects." In the years of 1981 & 1982, Martin imported partially assembled Sigma guitars from Japan and the assembly was completed in Nazareth, Pennsylvania.